<template>
  <div>
    <div class="todo-footer" v-show="total">
        <label>
        <input type="checkbox" :checked="isAll"  @click="selectAll(!isAll)"/>
        </label>
        <span>
        <span>已完成{{ doneTotal }}</span> / 全部{{ total }}
        </span>
        <button class="btn btn-danger" @click="deleteAllDone">清除已完成任务</button>
    </div>
  </div>
</template>

<script>
    export default {
        name: "MyFooter",
        computed:{
            isAll(){
                // 判断是否全部选中
                // if(this.todos.length === 0) return false
                return this.todos.length == this.doneTotal
            },
            total(){
                return this.todos.length
            },
            //计算出 已经完成的任务数
            doneTotal(){
                return this.todos.reduce((pre,todo) => {
                    return pre + (todo.completed ? 1 : 0)
                },0) 
            }
        },
        methods:{
            selectAll(isAll){
                this.$emit('selectAll',isAll)
            },
            deleteAllDone(){
                this.$emit('deleteAllDone')
            }
        },
        props:['todos']

    }
</script>

<style scoped>
    /*footer*/
    .todo-footer {
        height: 40px;
        line-height: 40px;
        padding-left: 6px;
        margin-top: 5px;
    }

    .todo-footer label {
        display: inline-block;
        margin-right: 20px;
        cursor: pointer;
    }

    .todo-footer label input {
        position: relative;
        top: -1px;
        vertical-align: middle;
        margin-right: 5px;
    }

    .todo-footer button {
        float: right;
        margin-top: 5px;
    }
</style>